It is known for self-contained computer workstations to be interconnected by a digital network. One advantage of such a network is that users of individual workstations can communicate with one another over the network, for example by means of a typed note, a data file or a program file transmitted to another user.
An important feature of systems providing user communication between workstations is that they should be `user-friendly`. In other words, it is desirable that the system should be able to be operated by a user who is not a skilled computer programmer.
The problem of inter-user communication is very similar to the problem of a single user maintaining communication between a number of concurrently running data processing tasks.
One approach at providing user-friendly interaction between different tasks running on a single workstation has been described by Henderson and Card in the article `Rooms: The Use of Multiple Workspaces to Reduce Space Contentions in a Window-Based Graphical User Interface` (ACM Transactions on Graphics, Vol.5, No.3, Jul. 1986, pages 211-243). This article describes a system in which a plurality of virtual workspaces, or `rooms` are defined in each of which a different task may be performed.
This prior art system makes use of the concept of a `door`. A door in this context is basically an icon which can be selected and which causes the workspace to be changed. When the user wishes to change room, he might well want to take some of the items being processed from one room to another. The article refers to these items as `baggage`. Despite the many advantages of the concept of `rooms`, the selection and transfer of baggage from one room to another can be rather cumbersome and time consuming processes.
As network capacities increase and better data compression techniques are developed, it is becoming more feasible to use the links provided by a computer network to transmit real-time sound or vision information between users and workspaces, which may well be running on other workstations. This has the potential for providing a more user-friendly means of communication between the workstation operators.
European Patent Application number 90300885.2 (UK9-89-041) describes a system in which a plurality of virtual data screens or rooms are defined. Distinct-anterior and posterior display layers are provided, with the anterior layer having a background such that the content of the posterior layer can be viewed therethrough. One of the layers is assignable for the display of a selected virtual screen, the other layer being dedicated to the display of an additional virtual screen. The system provides for the transfer of objects between the anterior and posterior display layers such that the dedicated layer can be used for transporting objects between workspaces. A facility is also described whereby one user can set up a shared vision channel with another user by selecting a door icon corresponding to that other user.
The workspaces can correspond to a single user or be shared `meeting workspaces`. In addition, a user can have a `private` workspace with more restricted access than his `public` workspace.
The `Timbuktu/Remote` software product, produced by Farallon Computing Incorporated for use on the Apple Macintosh computer, provides an on-screen `button` mechanism for accessing different workspace environments. The user can select (for example by means of a mouse-driven pointer or cursor) one of three buttons, which initiate varying degrees of access to another workspace. In particular, the three buttons are labelled `ATTENTION`, `OBSERVE`, and `CONTROL`, respectively providing means for gaining the attention of the other user, means for observing the other workspace, and means for controlling the other workspace.